In 1999, Guymon had his first professional fight against Zach Turnage with the fight resulting in a draw after fighting in three five-minute rounds and a five-minute overtime. He won two straight before opening the eyes of the matchmaker for the King of the Cage promotion who offered him a fight against up and comer, Diego Sanchez. Guymon took the fight and lost by armbarsubmission with three seconds left in the first round. Guymon's next four fights came inside the King of the Cage promotion all wins and all of them coming by submission in the first round. With the four wins he improved his overall record to 6-1-1 getting him signed to the IFL. He made his debut taking on Pat Healy losing via a split decision. Guymon then returned to King of the Cage and won five straight fights, the last one being for the King of the Cage Welterweight Championship just three weeks after his suicide attempt.
Four days after defending the King of the Cage Welterweight Championship against Quinn Mulhern, Guymon received a call from the UFC about signing a contract. Guymon accepted and signed onto a four-fight deal. He lost his UFC debut on January 11, 2010 in Fairfax, Virginia at UFC Fight Night 20 against 20-year-old Canadian, Rory MacDonald. The fight stayed standing for the most part but ended when Rory took the fight to the ground and submission submitted Guymon with an armbar near the end of the first round. Guymon defeated Yoshiyuki Yoshida on May 8, 2010 at UFC 113 by unanimous decision. Guymon faced Daniel Roberts on October 23, 2010 at UFC 121. Guymon would go on to lose the fight after Roberts locked on an anaconda choke, following with a gator roll that tightened the squeeze forcing Guymon to tap. Guymon next faced DaMarques Johnson on January 22, 2011 at UFC Fight Night 23 where he was injured early into the fight. He lost via verbal submission in the first round. After the fight, due to rupturing two discs in his back, Guymon announced his retirement from MMA.
Post-UFC
Guymon came out of retirement on March 16, 2012 dropping down to the Lightweight division where he defeated Chris Leyva by TKO due to punches in the second round at BAMMA USA: Badbeat 5. In his second fight at Lightweight in Bamma USA he beat Mike Dizack by split decision. Guymon faced Savant Young at Bellator 85. He suffered the first knockout loss of his career after a left hook from Young put Guymon out cold, just under a minute into the second round. After the fight, Guymon was taken to the hospital, where the doctor noticed he had fracture of the orbital, cheekbone and jaw. The doctor advised Guymon to never compete again in any combat sport. Days after his first Bellator win against Aaron Miller on November 2, 2013, Guymon announced his retirement from MMA for the second time.
Personal life
Mike Guymon is currently married to Nicole Guymon.
Suicide attempt
On August 11, 2009, Guymon attempted to commit suicide after a dispute with his wife about possibly divorcing. Guymon wrote his family a suicide note and had planned to shoot himself with a handgun, but before he could do so, his wife was able to wrestle the gun away. Guymon then got into his truck and drove away but was stopped a few blocks away by the Orange County Sheriffs Department. Guymon tried numerous times to get the deputies to shoot and kill him but all refused. The deputies were able to calm Guymon down and get him some help.
